Two nearly complete mitogenomes of wheat stem borers, Cephus pygmeus (L.) and Cephus sareptanus Dovnar-Zapolskij (Hymenoptera: Cephidae): An unusual elongation of rrnS gene

•We have characterised two nearly complete mitogenomes of wheat stem borers, Cephus pygmeus and Cephus sareptanus.•The general genome structure was mostly consistent with other hymenopteran species.•One translocation and one swapped position of tRNA genes were observed.•An unusual elongation in rrnS gene was reported for the first time for all known hymenopteran species.•A deviation from strand asymmetry was observed on the J-strand.

Two nearly complete mitochondrial genomes (mitogenomes) of wheat stem borers, Cephus pygmeus and Cephus sareptanus (Hymenoptera: Cephidae), were sequenced, characterised and compared with the previously known mitogenome of Cephus cinctus. The gene orders are mostly conserved, except for translocation of trnM and swapped position of trnI and trnQ. An A + T bias was found, but a deviation from strand asymmetry was also detected on the J strand. All protein coding genes (PCGs) are initiated by ATN codons, except for nad1, nad2 and atp8, and all are terminated with TAA, TA − or T − as a stop codon. The predicted secondary structures of rrnS and rrnL genes are mostly consistent with reported hymenopteran species. However, an unusual elongation in rrnS, not know elsewhere in the order, was discovered in Cephus species. Three autonomous sequences detected in domains I and II are mainly responsible for the length expansions.